# 方法一：
# for num in range(10,20):
#     for i in range(2,num):
#         if num%i == 0:
#             j = num/i
#             print('%d 等於 %d * %d' % (num,i,j))
#             break
#     else:
#         print(num,'是一個質數')

# 方法二：
i = 2
while(i < 100):
    j = 2
    while(j <= (i/j)):
        if not(i%j): break
        j = j + 1
    if(j > i/j): print(i,"是素数")
    i = i + 1
print("Good bye!")